The invention relates to a retention assembly for a cutting bit. More particularly, the invention pertains to a retention assembly for retaining a cutting bit holder (or tool holder) in a support block (or base) during use wherein the cutting bit holder carries the cutting bit.
Mining machines and construction machines (e.g., a road planing machine or road milling machine) are useful in continuous mining or road milling applications to mine or mill earth strata such as, for example, coal, asphalt, concrete and the like. These mining machines and construction machines utilize cutting bit assemblies. Each cutting bit assemblies for continuous mining or road milling applications typically comprises a cutting bit rotatably mounted within a support block. In turn, the support block mounts, typically by welding, on a drum or other body, wherein a suitable power source (or means) drives the drum. When a number of such support blocks carrying cutting bits are mounted onto a drum, and the drum is driven, the cutting bits will impinge and break up the earth strata into many pieces (i.e., cutting debris). Skilled artisans know the general operation of such a mining machine or construction machine. U.S. Pat. No. 7,144,192 to Holl et al. for a SELF-PROPELLED ROAD MILLING MACHINE, U.S. Pat. No. 7,370,916 to Ley et al. for a REAR LOADER ROAD MILLING MACHINE WITH HEIGHT-ADJUSTABLE SEALING DEVICE, and U.S. Pat. No. 7,070,244 to Fischer et al. for a ROAD MILLING MACHINE are exemplary patent documents that disclose such mining machines and/or construction machines.
During operation of the mining or construction machine, the support block experiences wear due to exposure thereof to the cutting debris. Over time, wear and other kinds of abuse causes the support block to become ineffective which signals an end to its useful life. Once this occurs, the operator must cut or torch the support block off the drum to allow for replacement of the support block. Typically, the operator welds the replacement support block on the drum. As the skilled artisan appreciates, it is time-consuming, and hence costly, to remove and replace a support block. Thus, there is an advantage to be able to prolong the useful life of the support block.
To prolong the life of the support block, one may use a cutting bit holder, sometimes referred to as a cutting bit sleeve, wherein the cutting bit rotatably or otherwise releasably mounts within the cutting bit holder. The cutting bit holder mounts within the support block via a mechanical connection. The presence of the cutting bit holder helps protect the support block from abuse and wear, thus minimizing or eliminating the periods of down time otherwise required for drum repair. The skilled artisan is aware of the use of cutting bit holders.
The skilled artisan is aware that cutting bits and cutting bit holders are subjected to considerable stresses during mining operations, road milling operations or other like operations. Accordingly, there is a desire to mount the cutting bit holder in the support block to minimize movement of the cutting bit holder in order to maximize the useful life of the cutting bit. It is also important that the mounting between the cutting bit holder and the support block be resistant to vibratory loosening which could likewise lead to premature cutting bit wear and failure. Heretofore, various structures exist to mount a cutting bit sleeve within a support block in an attempt to minimize cutting bit holder movement or loosening, while maximizing cutting bit life.
A mining machine or a road milling machine operates typically in severe operating conditions. During operation, the cutting bit holder (or tool holder) and/or the support block (or base) can experience damage such that it is difficult to disassemble these components. It is an advantage to be able to disassemble the cutting bit holder from the support block. Thus, it would be highly desirable to provide a cutting bit holder-support block assembly that facilitates a relatively easy disassembly of the cutting bit holder from the support block. Further, during operation, the severe operating conditions can also cause the rotatable cutting bit to lodge in the bore of the cutting bit holder. It would be advantageous to disassemble the cutting bit from the cutting bit holder. Thus, it is highly desirable to provide a cutting bit-cutting bit holder assembly that facilitates the relatively easy disassembly of the cutting bit from the cutting bit holder.
The following patent documents are exemplary of these various structures: U.S. Pat. No. 5,067,775 to D'Angelo for RETAINER FOR ROTATABLE BITS; U.S. Pat. No. 6,129,422 to Siddle et al. for a CUTTING TOOL HOLDER RETENTION SYSTEM; U.S. Pat. No. 5,769,505 to Siddle et al. for a CUTTING TOOL HOLDER RETENTION SYSTEM; U.S. Pat. No. 6,220,671 to Montgomery, Jr. for a CUTTING TOOL HOLDER RETENTION SYSTEM; U.S. Pat. No. 6,234,579 to Montgomery, Jr. for a CUTTING TOOL HOLDER RETENTION SYSTEM; U.S. Pat. No. 6,331,035 to Montgomery, Jr. for a CUTTING TOOL HOLDER ASSEMBLY WITH PRESS FIT; U.S. Pat. No. 3,749,449 to Krekeler for a MEANS FOR REMOVABLY AFFIXING CUTTER BIT AND LUG ASSEMBLIES TO DRIVER ELEMENT OF A MINING MACHINE OR THE LIKE; U.S. Pat. No. 4,650,254 to Wechner for a BIT HOLDER; and U.S. Pat. No. 5,607,206 to Siddle et al. for a CUTTING TOOL HOLDER RETENTION SYSTEM.